More than beginning or end of brake zone, I try and be more mindful of trying to have a good amount of overhead in the rev range while downshifting. I like to make sure that when I go down a gear, the RPM of the next gear down isnt in to the rev limiter or close, just doing what I can to go a bit easy on the motor.
Here is a good video of me going 6 to 3 in the NBY Nissan at VIR last summer. You can see my brake pressure isn't the most consistent as I heel/toe. I would be curious what sort of percent change I'm creating from that "nominal" brake pressure vs what happens when I go for the throttle to grab the next gear down.

Adding downforce while limiting drag. We all want huge wings and giant splitters, but those come at a cost, drag. As budget racers, how can we get an idea of how much drag we're adding? Most reputable wings will come with that data, but what about a homemade plywood splitter?